SOME SAMPLE FAMILIES

61

family Palceotheriidcz, besides containing that side-
branch of the horse-lineage, Palceotherium, also in-
cluded the Miocene Anchitherium and other " middle
horses," while the family Equidas was taken as starting

RECENT

Equus
Tapirus
Rhinoceros

PLEISTOCENE

I
i 4 l
' Hippidmm Equus l\
1
5
Rhinoceros

PLIOCENE
Chalicotherium 1 1
\ 1 \ / \ , \ '
PUohtppus /
^ Hipparioa '

MIOCENE
1 Chalicotherium
1 I
Moropus 1
,. \X Protohippus JVlcrychippus / " \ ' \ / \ \ /

Acerathenum Tclcoceras
s
Baluchithcrium

Parahippus Anchithenum I

OLIGOCENJ V
Moropus X""Q" I / 0
i Brontops
1 ' l I
Minhippus ^ /
M '
Palzothcr: / .X^Colodon
1
N^Tapirus
\/ Hyracodon
/ / Metan^ynodon Coenopus ^ s

I EOCENE
\Wf
/ t L j \ >^ /Prothyraiodoty ^ \ /p , Lophiodon ' IN./ A If
V \ , f \ ^ Hclate cs / N. / / / APalaoth\ N \ / ' N/ x X
XLambdotN^V g > \ / / \ > ~" "~ - \ \ Homogalax

PALEOCEN
x v \ Tetrad* nodon "^- \ ,''

FIG. 7.—CLASSIFICATION OF PERISSODACTYLS BY LYDEKKER, 1889,
PARTLY c; VERTICAL/' PARTLY <c HORIZONTAL."

Families recognized: i, Tapiridffi; 2, Lophiodontid^; 3, Paljeo-
theriidae; 4, Equidae; 5, Rhinocerotidse; 6, Lambdotheriidse; 7,
Chalicotheriidae; 8, Titanotheriidje.

in the late Miocene with Protohippus and Merychippus.
Family divisions were, in fact, " transverseJ) as well as
" vertical." In Figs. 7 and 8 I have indicated the differ-
ence between these two methods of classification. The